Real-Space Evidence of Rare Guanine Tautomer Induced by Water

Water is vital for life as a solvent. Specifically, it has been well established that DNA molecules are hydrated in vivo, and water has been found to be responsible for the presence of some noncanonical DNA base tautomers. Theoretical investigations have shown that the existence of water could significantly influence the relative stability of different DNA base tautomers, reduce the energy barrier of tautomeric conversions, and thus promote the formation of some rare base tautomers. In this work, we report the real-space experimental evidence of rare base tautomers. From the high-resolution scanning tunneling microscopy imaging, we surprisingly find the formation of the rare guanine tautomer, <i>i.e.</i>, G/(3H,7H) form, on the Au(111) surface by delicately introducing water into the system. The key to the formation of this rare tautomer is proposed to be the “water bridge” that largely reduces the energy barriers of intramolecular proton-transfer processes as revealed by extensive density functional theory calculations. The real-space experimental evidence and the proposed mechanism make a step forward toward the fundamental understanding of water-assisted base tautomerization processes

Exploring the Self-Assembly Behaviors of an Organic Molecule Functionalized by Terminal Alkyne and Aldehyde Groups on Au(111)

On-surface self-assembly from molecular building blocks directed by supramolecular interactions has been widely reckoned as an efficient method for controllable construction of low-dimensional nanostructures and nanomaterials. Numerous efforts have been devoted to exploring the self-assembled behaviors of molecular precursors on different surfaces and unravelling the underlying mechanism. Generally, the molecular precursors are functionalized with one kind of functional groups for directing the self-assembly. In this study, by combining real-space direct visualization and DFT calculations, we have investigated the self-assembly behaviors of an organic molecule functionalized by two different functional groups: terminal alkyne and aldehyde groups on Au(111). An ordered racemic island nanostructure is formed on Au(111), which results from the hybrid interactions between the two functional groups. Detailed DFT calculations have been performed to compare the different binding ways and binding strengths between the organic molecules